From 130d199e6e25d49ae6211705eddf0bedf42dc914 Mon Sep 17 00:00:00 2001
From: Ronan Abhamon <ronan.abhamon@belledonne-communications.com>
Date: Mon, 21 May 2018 11:53:19 +0200
Subject: [PATCH] fix(StaticString): add a workaround for MSVC 2015 on int
 constructor

---
 include/linphone/utils/static-string.h | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/include/linphone/utils/static-string.h b/include/linphone/utils/static-string.h
index de5bae91f..bbc421e06 100644
--- a/include/linphone/utils/static-string.h
+++ b/include/linphone/utils/static-string.h
@@ -111,18 +111,16 @@ namespace Private {
 		RawStaticString<N> raw;
 
 	private:
-		template<typename T>
-		static constexpr bool testInt (T n) {
-			// Do not use it directly in the two enable_if below. (MSVC 2015 bug.)
-			return n < 0;
-		}
+		// Workaround for MSVC 2015.
+		// See: https://stackoverflow.com/questions/41593649/why-wont-visual-studio-let-me-use-a-templatized-constexpr-function-in-enable-i/41597153
+		struct IsNeg { static const bool value = Value < 0; };
 
-		template<std::size_t... Index, typename Int = int, typename std::enable_if<!testInt<Int>(Value), int>::type* = nullptr>
+		template<std::size_t... Index, typename Int = int, typename std::enable_if<!IsNeg::value, Int>::type* = nullptr>
 		constexpr StaticIntStringHelper (const IndexSequence<Index...> &) :
 			raw{ char('0' + Value / pow10(N - Index - 2) % 10)..., '\0' } {}
 
-		template<std::size_t... Index, typename Int = int, typename std::enable_if<testInt<Int>(Value), int>::type* = nullptr>
-		constexpr StaticIntStringHelper (const IndexSequence<Index...> &) :
+		template<std::size_t... Index, typename Int = int, typename std::enable_if<IsNeg::value, Int>::type* = nullptr>
+		constexpr StaticIntStringHelper(const IndexSequence<Index...> &) :
 			raw{ '-', char('0' + abs(Value) / pow10(N - Index - 3) % 10)..., '\0' } {}
 	};
 };